1. Field of the Invention
The present invention is in the field of solar energy and specifically relates to a control system for maximizing the power output of a solar array by altering the direction in which it is pointing, to compensate for movement of the sun, and other factors affecting total insolation
2. The Prior Art
A first group of patents make use of an open loop pointing system, in which the array is pointed to a direction at which the sun should be at a particular time. These patents include: U.S. Pat. No. 4,546,756 to Leroy, et al., U.S. Pat. No. 4,536,897 to Erickson, et al.; U.S. Pat. No. 4,440,150 to Kaehler; and, U.S. Pat. No. 4,215,410 to Weslow, et al.
A second group of patents show seekers of various designs that, typically, are mounted on the array and that include their own detectors.
In U.S. Pat. No. 4,352,350 Johnson shows a piston in a cylinder that is driven one way or the other depending on which side of the center the focus falls on.
In U.S. Pat. No. 4,564,275, Stone shows a control system for a heliostat. A digital image radiometer observes the target illuminated by the sun beam reflected from the heliostat mirror to determine whether the beam is centered or whether there is a pointing error. Having determined the error, the system corrects it.
In U.S. Pat. No. 4,287,411 Benucci shows a seeker that uses four photocells to provide error signals in two angular dimensions.
As shown in FIGS. 5 and 6 of U.S. Pat. No. 4,267,441, Monk shows a receiving means which consists of a narrow slit to pass light into a housing in which are located two detector cells. This is essentially a pinhole camera. There is a small inactive strip between the cells of the differential detector.
In U.S. Pat. No. 4,225,781, Hammons shows a solar tracking apparatus that is mounted on the array as shown in his FIGS. 1-3.
In U.S. Pat. No. 4,187,123, Diggs uses an array of four thermocouples which normally lie in the shadow of member 71 shown in FIG. 8.
In U.S. Pat. No. 4,146,784, Yekutieli uses a novel type of seeker shown in his FIGS. 2a and 2b to provide steering information.
In U.S. Pat. No. 4,107,521, Winders shows a seeker in which a shaded light sensor is used. The sensor is a light-activated SCR.
In U.S. Pat. No. 4,649,899, Moore uses three elongated shadow boxes as a seeker, in the manner shown in his FIG. 2.
In U.S. Pat. No. 3,699,324, liff, et al. show a tracking system that points the boresight to a computed future position, and then allows the source to drift through the conical tracking beam.
The above-described patents describe seekers that perform best when attempting to locate bright point sources against a dark background. Their performance is difficult to analyze and not always reliable when called upon to track extended sources or to distinguish sources from a bright background.
The above patents typically employ seekers that are mounted on or adjacent the solar panel and the seeker includes its own detector. As will be seen below, the present invention does not employ a separate seeker or additional detectors. Instead, the solar panel itself is used as the detector.
None of the above patents addresses the problem of maximizing the power output of the solar array.
As will be seen below, the system of the present invention overcomes these problems of the prior art systems and maximizes the output of the solar array by the use of a simple and effective control system.